Examples of preparation of tetrahydrogenated .alpha.-pyrones have already been given in literature. Mention may be made for example of the preparation of 4,4,6-trimethyl 3-phenyl 2-tetrahydropyrone (R. LONGERAY and J. DREUX in Bull. Soc. Chim. Fr. 1963, 2805) or the preparation of 6-methyl 3,4-diphenyl 3,4,5,6-tetrahydro-2-pyrone (A. M. BARADEL, R. LONGERAY and J. DREUX, Bull. Soc. Chim. Fr. 1970, 255). The process described in these publications are long and complicated and further have the disadvantage of a poor overall yield, hardly exceeding 1%, which in practice forbids the manufacture of these derivatives on the industrial scale, by reason both of the difficulties of preparation and of the lack of economic profitability.